ranzcrpart1fandomcom-20200214-history
Venous
The cerebral veins drain the brain parenchyma and are located in the subarachnoid space. They pierce the meninges and drain further into the cranial venous sinuses. Unlike the cortical arteries that runs deep in the sulcus, cortical veins travel superficially. The cerebral veins lack muscular tissue and valves. The cerebral venous system can be divided into: * Superficial ("external") veins (3 subgroups). Located in the SAS/cisterns. ** Superior group: *** 8-12 smaller cortical veins over hemispheres, *** vein of Trolard ** Middle group: *** superficial middle cerebral vein *** vein of Labbé ** Inferior group: *** deep middle cerebral vein *** basal vein of Rothensal * Deep ("internal") veins ** Subependymal veins ** internal cerebral veins (formed by thalamostriate, septal veins) ** Great cerebral vein Venous vascular territories * More variable, less well-known than arterial territories * General concepts ** Venous drainage generally radial, centrifugal (exception = deep cerebral structures) ** Much of middle/superior brain surfaces (cortex, subcortical white matter) drained by cortical veins to superior sagittal sinus. ** Posterior/inferior temporal lobe, adjacent parietal lobe drained by vein of Labbé to transverse sinus. ** Insular cortex, parenchyma around sylvian (middle cerebral) fissure drained by sphenoparietal sinus to cavernous sinus. ** Deep cerebral structures (central/deep white matter, basal ganglia) drained by medullary/subependymal veins to internal cerebral veins, great cerebral vein, straight sinus; medial temporal lobe via deep middle cerebral vein/basal vein of rothensal to great cerebral vein. * Anatomy Relationships ** Anastomotic veins *** Have reciprocal relationship (if one is large, others typically smaller or absent) *** Abundant anastomoses with each other as well as deep (internal) cerebral veins, orbit, extracranial venous plexi Superficial venous system The superficial venous system comprises the sagittal sinuses and cortical veins. The cortical veins course along the cortical sulci, drain the cortex and some of the adjacent white matter. There are numerous cortical veins and most of them are unnamed, however the large cortical veins can be identified and according to their locations cortical venous system can be subdivided into superior, middle and inferior groups. * Superior group: ** 8-12 smaller superior cerebral veins, drain the superior portion of the cerebral cortex. They run up in the sulci and enter the superior sagittal fissure at right angles. ** vein of Trolard. ** Vascular territories include: superolateral hemispheric surfaces, most of medial hemispheric surfaces between ISS and SSS, most of frontal lobes except for perisylvian area * Middle group: ** Superficial middle cerebral vein: passes along the Sylvian fissure and drains the cortex around it. It curves anteriorly around the tip of the temporal lobe and drains into the sphenoparietal sinus or cavernous sinus. Its posterior end have connections for other dural venous sinuses by anastomotic veins which are: *** to the superior sagittal sinus by the great anastomotic vein of Trolard *** to the transverse sinus by the posterior anastomotic vein of Labbé ** Vascular territories: perisylvian area, anterior temporal lobes, with the Vein of Labbe draining posterior temporal and lower parietal lobes. * Inferior group ** Mostly anastomose with the deep venous system ** Inferior cerebral veins: drains the inferior surface the cerebral hemisphere into the nearby sinuses, e.g. cavernous, superior petrosal and transverse sinus. ** Basal vein of Rosenthal: Inferior insula, basal ganglia, medial temporal lobes ** Orbital surface of frontal lobe drains superiorly to superior sagittal fissure. Deep venous system The deep venous consist of lateral sinuses, sigmoid sinuses, straight sinus and draining deep cerebral veins (subependymal and medullary veins). * Medullary veins - small, linear veins originate 1-2 cm below cortex. Course towards ventricles, terminate in subependymal veins. The medullary veins are arranged in a wedge shaped manner. * Subependymal veins - they receive medullary veins and aggregate into greater tributaries. They run under ventricular ependyma, define ventricular margins ** The internal cerebral vein: lies on the roof of the third ventricles, is formed at the interventricular foramen by *** the choroidal vein (draining the choroid plexus of the lateral ventricle) *** thalamostriate vein (drain caudate nucleus and thalamus). ** The basal vein, AKA vein of Rosenthal ''passes lateral to the cerebral peduncle from the medial surface of the temporal lobe through the ambient cistern to drain into the vein of Galen. It is closely related to the posterior cerebral artery (PCA). It is formed by *** The anterior cerebral vein (drain genu of the corpus callosum and orbital portion of the frontal lobe) *** deep middle cerebral vein (drain lateral sulcus and insula) *** striate veins'' (drain corpus striatum) ** The vein of Galen, AKA the great cerebral vein, is a short trunk formed by the union of the two internal cerebral veins and basal veins of Rosenthal. It curves backward and upward around the splenium of the corpus callosum and ends at the confluence of the inferior sagittal sinus and the anterior extremity of the straight sinus. Both of these systems mostly drain into internal jugular veins. Generally, venous blood drains into the nearest venous sinus or, in the case of blood draining from the deepest structures, into deep veins